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Emprical Formula

Discussion in 'DAT Discussions' started by Dencology, May 28, 2008.

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  1. Dencology

    Dencology
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    A compound consist of carbon, hydrogen, and oxygen is known by quantitative analysis to have 55.2% oxygen and 3.4% hydrogen by mass. what is the empirical formula?
    guys, if the mass of Carbon is not given how do we do this? i know that some people just do this calculation by looking at the choices. Like the amount of Oxygen is almost half the amount of the compound therefore, carbon needs to be a little less or almost the same amount as oxygen.

    a. CHO
    b. CH2O
    c. CH3O
    d. C2H6O2
    e.CH4

    the answer is A. but how can we do this without calculation so we can speed up.
     
    #1 Dencology, May 28, 2008
  2. Zerconia2921

    Zerconia2921 Bring your A-game!
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    If the carbon isnt given it can stll be calculated because the percent is out of 100. We have 55.2% + 3.5% = 58.7% So 100%-58.7%=41.3% of Carbon

    oxygen .552/16g/mol = .03mol, hyrogen .035/1g/mol = .03mol, carbon .413/12g/mol = .03mol

    0.03mols/0.03mols = 1

    CHO answer A
     
    #2 Zerconia2921, May 28, 2008
  3. OP
    OP
    Dencology

    Dencology
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    thanks.
     
    #3 Dencology, May 28, 2008
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